EP 1 074 322 A1 has disclosed a rotating chuck that is embodied in the form of a shrink fit chuck for a tool, in particular for a drill bit or milling bit. This rotating chuck has a coolant supply conduit. The shrink fit chuck has a receiving bore for the tool in which the tool is secured by means of a shrink fit seat during operation. The receiving bore has a number of axially extending longitudinal grooves distributed around its inner circumference, which are connected to the supply conduit for a coolant. The grooves extend to the free end of the shrink fit chuck and feed into the open air there. In terms of their cross-section, the grooves are embodied as narrow grooves. In a shrink lit chuck of this kind, it has been observed that particularly at high rotation speeds that occur during operation of the chuck and particularly with small tool diameters, the jet of coolant emerging from the end separates from the tool and a reliable supply of coolant to the cutting region is not always guaranteed, particularly with longer tools. Due to this narrow embodiment of the grooves, the coolant emerges in the form of three separate jets. This, too, does not always guarantee a reliable cooling of the tool in the cutting region/material-removing region.
DE 198 32 793 134 has disclosed a tool holding device embodied in the form of a collet in which the coolant is conveyed on the inside of the tool holding device, through slots of the collet, past the tool shank, to the free front end of the tool holding device. A covering cap with an insert rests against this free front end; the insert forms an annular gap through which the coolant can travel out into the open air from the inside of the tool holding device.
The exit of the coolant into the open air here occurs in a relatively indefinite fashion and cannot always guarantee a clean guidance of the coolant jet along the tool. In addition, a tool holding device according to DE 198 32 793 B4 requires a significant coolant flow rate, which in turn requires coolant pumps with high pumping capacities.
DE 693 31 325 T2 has disclosed a tool holding system embodied in the form of a shrink fit chuck in which a receiving opening, for a cylindrical tool is provided with longitudinal grooves through which the coolant can be conveyed. The longitudinal grooves are cross-sectionally embodied in the form of narrow moves with a rounded groove bottom.
FR 22 39 849 has disclosed a tool holding device in which a receiving opening for a tool is likewise provided with longitudinal grooves through which a coolant can be conveyed. The grooves are cross-sectionally embodied in the form of narrow grooves with a square groove bottom. As a result, the coolant emerges into the open air in the form of bundled jets. This is not desirable.
The object of the present invention, therefore, is to disclose a tool holding device, in particular a tool holding device embodied in the form of a shrink fit chuck, in which the coolant guidance inside the tool holding device is optimized and in particular when the coolant emerges from the tool holding device, a coolant envelope that is closed or essentially closed in the circumference direction around a rotating tool can be formed, which rests against the tool and/or the tool shank. In particular, measures should be disclosed that make it possible to guide the closed or essentially closed coolant envelope around the rotating tool as close to the tool as possible, i.e. in as bundled a fashion as possible, even at high rotation speeds when it is subject to centrifugal forces, and to minimize or prevent a mushrooming, or dispersing of the coolant envelope around the tool. The coolant can be embodied in the form of all types of fluids, in particular a liquid, a gas, or a gas/oil mixture (oil mist).
Another object of the invention is to ensure the most efficient possible cooling defined at the locations in which the material-removing machining is occurring with the lowest possible volumetric flow rate of coolant.
Another object of the invention is to disclose a tool holding device that enables coolant to emerge from the device with no tangential velocity, with almost no tangential velocity, or with at least reduced tangential velocity at a predetermined operating rotation speed.
Another object of the invention is to provide a closed coolant envelope around the machining tool (rotating tool) with a satisfactory jet guidance, without having to accept excessive limitations with regard to the maximum usable tool length.